Dipendra project

“Eddy Current Breaks”
A
Seminar Report
Submitted
In partial fulfillment
For the awarded of the degree of
Bachelor of Technology (B. Tech)
IN DEPARTMENT OF ELECTRICAL ENGINEERING
GUIDED BY: SUBMITTED BY: -
Mr. Kishore Thakre Dipendra Singh
2017UEE008
DEPARTMENT OF ELECTRICAL ENGINEERING
ENGINEERING COLLEGE, JHALAWAR
RAJASTHAN TECHNICAL UNIVERSITY, KOTA
September, 2020

i
CANDIDATE DECLARATION
I hereby declare that the work, which is being presented in this seminar entitled “Eddy Current
Breaks” in partial fulfillment of requirement for the award of degree of “Bachelor of
Technology” in Department of Electrical Engineering, Engineering College Jhalawar,
Rajasthan Technical University, Kota is a record of my own investigations carried under the
Guidance of Mr. Kishore Thakre, Department of Electrical Engineering, Engineering College
Jhalawar.
(Name and Signature of candidate)
Dipendra Singh
(2017UEE008)
Counter Signed By
Mr. Kishore Thakre
(Assistant Professor)
Department of Electrical Engineering,
Engineering College Jhalawar
Rajasthan Technical University, Kota

ii
आभिय ांत्रिकी मह विध लय झ ल ि ड़ ENGINEERING COLLEGE JHALAWAR
{र जस्थ न सरक र क स्ि यत्तश सी सांस्थ न} (An AutonomousInstitutionofGovernmentofRajasthan)
सुनेल रोड, झ लर प टन, झ ल ि ड़, र जस्थ न-326023 Sunel Road, Jhalrapatan, Jhalawar, Rajasthan-326023
टेलीफ़ोन+91-07432-242811,242812 Tel-No. +9107432-242811,242812
ए-मेल principalgecj@gmail.com Email:principalgecj@gmail.com
िैबस इट www.gecj.ac.in Website:www.gecj.ac.in
CERTIFICATE
This is to certify that this seminar report entitled “Eddy Current Breaks” has been successfully
carried out by Dipendra Singh for the partial fulfillment of award of Bachelor of Technology
from Engineering College, Jhalawar under my supervision.
Mr. Kishore Thakre
(Assistant Professor)
Department of Electrical Engineering,
Engineering College Jhalawar
Rajasthan Technical University, Kota
Date: -

iii
ACKNOWLEDGEMENT
First of all, we would like to express my deep sense of gratitude to our Guide Mr. Kishore Thakre
Department of Electrical Engineering for his active cooperation in completion of this work. He
was kind enough to cater my never-ending queries. Without his gracious cooperation and valuable
guidelines, the work would not have been in present shape.
For the accomplishment of this seminar work, expression and words run short to convey my
gratitude to many individuals. This report work is an outcome of moral support and persuasive
interest dedicated from many individuals directly or indirectly involved. We are highly indebted
and grateful to Other Faculty members name and other faculty members in the electrical
department at (ECJ) Engineering College Jhalawar for their continuous blessings and
encouragement.
Last but not the least; we would like to express our gratitude to our parents for their valuable
support and encouragement.
(Name and Signature of candidate)
Dipendra Singh
(2017UEE008)

iv
ABSTRACT
This is an electric braking system which works on the principle that eddy current produced in it
opposes the driving torque. This opposing torque is used to break the automobiles. Mainly this
system is purely based on Faraday’s laws of electromagnetic induction and Lenz’s law. For
operating this a control switch is provided on the steering column in a position for easy manual.
The skidding and complexity of mechanical braking system can be minimized by this system.
Also, the wear and tear of the vehicles can be reduced. Since researches are going on to eliminate
some of the disadvantages of this system, we can accept it to be the norm one in a few years of
time.

v
CONTENTS
Candidate declaration I
Certificate ii
Acknowledgement iii
Abstract iv
Contents v
List of Figures vi
List of Abbreviations vii
CHAPTER – 1 INTRODUCTION
1.1Introduction
1.2 Principal of operation
1-2
1
2
CHAPTER – 2 CONSTRUCTION 3-4
CHAPTER – 3 WORKING 5-6
CHAPTER – 4 EDDY CURRENT BRAKES IN TRAIN 7-8
CHAPTER – 5 TYPES OF EDDY CURRENT
5.1 Electrically Excited eddy current brakes
5.2 Permanent Magnet eddy current brakes
9-12
9
12
CHAPTER – 6 EDDY CURRENT BRAKES
REQUIRMENT
13
CHAPTER – 7 ADVANTAGES 14
CHAPTER – 8 DISADVANTAGES 15
CHAPTER – 9 APPLICATION 16

vi
CONCLUSION 17
REFERENCES 18
LIST OF FIGURES
Fig No. Name of Figure Page No.
Fig.1.1 Eddy Current induced in a conductor 2
Fig.4.1 Eddy Current breaks in train 7
Fig.4.2 Distribution of magnetic flux density 8
Fig.5.1 electrically excited eddy current break 10
Fig.5.2 Braking Power Calculation 11

vii
LIST OF ABBREVIATIONS
R Resistance
Mm Millimeter
IEEE Institute of electrical and electronics engineering
EMF Electromotive force

1
Chapter 1
INTRODUCTION
1.1 Introduction
Many of the ordinary brakes, which are being used now days stop the vehicle by means of
mechanical blocking. This causes skidding and wear and tear of the vehicle. And if the speed of
the vehicle is very high, the brake cannot provide that much high braking force and it will cause
problems. These drawbacks of ordinary brakes can be overcome by a simple and effective
mechanism of braking system ‘The eddy current brake’. It is an abrasion-free method for braking
of vehicles including trains. It makes use of the opposing tendency of eddy current.
Eddy current is the swirling current produced in a conductor, which is subjected to a change in
magnetic field. Because of the tendency of eddy currents to oppose, eddy currents cause energy to
be lost. More accurately, eddy currents transform more useful forms of energy such as kinetic
energy into heat, which is much less useful. In many applications, the loss of useful energy is not
particularly desirable. But there are some practical applications. Such an application is the eddy
current breaks.
1.2Principle of Operation
Eddy current brake works according to Faraday’s law of electromagnetic induction. According to
this law, whenever a conductor cuts magnetic lines of forces, an emf is induced in the conductor,
the magnitude of which is proportional to the strength of magnetic field and the speed of the
conductor. If the conductor is a disc, there will be circulatory currents i.e. eddy currents in the disc.
According to Lenz’s law, the direction of the current is in such a way as to oppose the cause, i.e.
movement of the disc.

2
Essentially the eddy current brake consists of two parts, a stationary magnetic field system and a
solid rotating part, which include a metal disc. During braking, the metal disc is exposed to a
magnetic field from an electromagnet, generating eddy currents in the disc. The magnetic
interaction between the applied field and the eddy currents slow down the rotating disc. Thus, the
wheels of the vehicle also slow down since the wheels are directly coupled to the disc of the eddy
current brake, thus producing smooth stopping motion.
Figure 1.1 Eddy Current induced in a conductor

3
Chapter 2
CONSTRUCTION
Essentially an eddy current brake consists of two members, a stationary magnetic field system
and a solid rotary member, generally of mild steel, which is sometimes referred to as the
secondary because the eddy currents are induced in it. Two members are separated by a short air
gap, they’re being no contact between the two for the purpose of torque transmission.
Consequently, there is no wear as in friction brakes.
Stator consists of pole core, pole shoe, and field winding. The field winding is wounded on the
pole core. Pole core and pole shoes are made of east steel laminations and fixed to the state of
frames by means of screw or bolts. Copper and aluminum are used for winding material the
arrangement is shown in fig. 1.1. This system consists of two parts:
1. Stator
2. Rotor
Stator: - It is supported frame members of the vehicle chassis. It has introduced magnetic poles
energized by windings. Current is supplied to the winding from the battery.
Rotor: - It is a rotating disc, which is fitted on the line of crankshaft with small air gap to stator.
When disc rotates a flux, change occur in the section of the disc passing the poles of stator. Due
to the flux change there is a circulatory or eddy current in the disc around the magnetic lines of
force. The effect of this eddy current induces ‘N’ and ‘S’ poles at the surface of the disc. Then
there will be a ‘drag’ or braking effect in between eddy current induced poles and magnetic poles
in the stator. By changing current from the battery, we can change the braking force. In this
braking system kinetic energy of the vehicle is converted to heat and dissipated through the
rotating disc.
Total resistance of field winding
R = L/A
where, L = total length of field winding in meter.

4
 = Resistivity of the wire in ohm meter
A = the area of cross section of field winding in m2
Total no: of terms = total length /mean length of one term
The rotor is a rotating disc on shaft, which is placed very near to the stator with small air
gap (1 mm to 2 mm). Rotating disc may be one or both side of stator.
The two units have common ring member, poles cores on which winding are provided
being fixed to ring number. If a malleable casting is employed, then the pole core could be cast
integrally with the right. After fitting the windings on the cores, poles shoes are fitted to provide
pole faces of appropriate shape and area. The rotor disc should be provided with properly designed
fins for faster heat removal. The magnetic circuits of the two units are substantially the same, non-
undue and thrust would be imposed on the motor bearings. Slight axial displacement of rotor could
however, cause quite appreciable discrepancy, the air gap of two units. The effect would be to
increase the magnetic pull in one air gap and diminish it on other which could give to rise to
excessive and thrust on rotor bearing to overcome the inherent defect, the air gaps of both units
could be put in series by making the central number nonmagnetic and providing a continues pole
core for each pair axially opposite poles. This modification could possibly reduce the length of
the combined pole course or permits a larger winding length.
The maximum diameter of the eddy current brake is decided by
1. The spacing of vehicle chassis frame.
2. Vehicle floor clearance.

5
Chapter 3
WORKING
When the vehicle is moving, the rotor disc of eddy current brake which is coupled to the wheels
of the vehicle rotates, in close proximity to stationary magnetic poles. When we want to brake the
vehicle, a control switch is put on which is placed on the steering column in a position for easy
operation.
When the control switch is operated, current flows from a battery to the field winding, thus
energizing the magnet. Then the rotating disc will cut the magnetic field. When the disc cuts the
magnetic field, flux changes occur in the disc which is proportional to the strength of the magnetic
field. The current will flow back to the zero field areas of the metal plate and thus create a closed
current loop like a whirl or eddy. A flow of current always means there is a magnetic field as well.
Due to Lenz’s law, the magnetic field produced by the eddy currents works against the movement
direction. Thus, instead of mechanical friction, a magnetic friction is created. In consequence, the
disc will experience a “drag” or the braking effect, and thus the disc stops rotation. The wheels of
the vehicle, which is directly coupled to the disc, also stop rotation. Faster the wheels are spinning,
stronger the effect, meaning that as the vehicle slows, the braking force is reduced producing a
smooth stopping action.
The control switch can be set at different positions for controlling the excitation current to several
set values in order to regulate the magnetic flux and consequently the magnitude of braking force.
i.e. if the speed of the vehicle is low, a low braking force is required to stop the vehicle. So, the
control switch is set at the lowest position so that a low current will be supplied to the field winding.
Then the magnetic field produced will be of low strength, so that a required low braking force is
produced. When the control switch is operated during the standby position of the vehicle, the
magnet will be energized and magnetic field is created. But since the wheels are not moving,
magnetic lines of force are not cut by it, and the brake will not work. However, a warning lamp is
provided on the instrument panel to indicate whether the brake is energized. This provides a safe
guard for the driver against leaving the unit energized. When control switch is put in any one of

6
the operating positions, the corresponding conductor in the contractor box is energized and current
flows from the battery to the field winding to the contractor box. This current magnetizes the poles
in stator, which placed very near to the rotor. When rotor rotates it will cut magnetic lines and
eddy current will set up in the rotor. The magnetic field of this eddy current produces a breaking
force or torque in the opposite direction of rotation disc. This kinetic energy of rotor is converted
as heat energy and dissipated from rotating disc to surrounding atmosphere. Current in the field
can change by changing the position of the controls switch. Thus, we can change the strength of
the braking force.

7
Chapter 4
EDDY CURRENT BREAK IN TRAIN
In the case of trains, the part in which the eddy current is induced is rail. The brake shoe is enclosed
in a coil, forming an electromagnet. When the magnet is energized, eddy currents are induced in
the rail by means of electromagnetic induction, thereby producing braking action.
Figure 4.1 Eddy current breaks in train

8
Figure 4.2 Distribution of magnetic flux density

9
Chapter 5
TYES OF EDDY CURRENT BRAKES
There are two types of eddy current brakes according to the method of excitation.
1.Electrically excited eddy current brake
2.Permanent magnet eddy current brake
5.1 Electrically Excited Eddy Current Brake
Electrically excited eddy current brakes are abruption-free method for braking. In high-speed trains
they offer a good alternative to the mechanical rail brakes which are being used now a days. During
braking, the brake comes in contact with the rail, and the magnetic poles of brakes are energized
by a winding supplied. Magnetic poles of brakes are energized by a winding supplied with current
from the battery. Then the magnetic flux is distributed over the rail. The eddy currents are
generated in the rail, producing an electromagnetic braking force. These types of braking need an
additional safety power supply when there are breakdowns in the electrical power supply.

10
Figure 5.1 electrically excited eddy current break
5.2 Permanent Magnet Eddy Current Brake
Recently, permanent magnet eddy current brakes have been developed for subways, trams and
local trains. These brakes need a mechanical actuator to turn the magnets in an on and off position.
The main advantage of this type of brake is safety. i.e. it does not need electrical power supply to
energize the magnet.

11
Figure5.2 Braking Power Calculation
Sophisticated calculation methods for the determination of braking forces of eddy current brakes
are important for the design of the brakes.
For a simple eddy current brake employing a thin non-magnetic disc as copper the drag or braking
force on the disc

12
where
H = Magnetic field strength in Weber.
A = Pole force area in cm2.
V = Velocity in cm/sec of mean radius of disc under the poles.
T = disc thickness in cm.
 = specific resistance of disc material at its operating temperature in micro ohms/cm3.
Torque = F * R Nm
Where R = mean pole radius in meter.
Power P = 2  NT/60 watts.

13
Chapter 6
EDDY CURRENT BRAKE REQUIREMENT
An eddy current brake is an energy converter functions is to convert the kinetic energy of a vehicle
into heat and dissipate it such a rate to maintain the temperature of unit within reasonable limits
under maximum and prolonged braking conditions. The energy absorbed by the brake is
transformed into heat by the currents induced in the motor, and this is heat manly dissipated in
surrounding air through the medium of suitable designed fins the rotating member.
In mountains area, continues braking force is needed for a long time (say about half an hour), at
this condition, eddy current braking is more suitable to function without overheating. The use of
these retarders is by no means limited to mountain on country. They can be advantageously
employed on public service vehicles on city routes without frequent stops. But in this braking
system there without be any braking force in the vehicle is rest. So, the eddy current brake is used
as an auxiliary heavy-duty retarder. By using auxiliary retarder very smooth retardation is assumed
and likely hood of skidding on slippery roads surfaces is minimized. Smooth braking action cuts
down tier were and since brake is used as an auxiliary heavy-duty retarder. By using auxiliary
retarder very smooth retardation is assumed and likely hood of skidding on slippery roads surfaces
is minimized. Smooth braking action cuts down tier were and since the conventional brakes are
relieved of heavy duty being required only to bring vehicles to rest.
6.1 Mounting and Installation
A typical mounting of an eddy current brake consists of two discs in which pole salient type,
supported between the frame numbers of a vehicle chassis. Rotor is coupled to road wheels being
often mounted on a shaft that is interposed between the gearbox and propeller shaft and stator is
mounted on the frame of the vehicle. The driver who can select one or four excitation settings
according to the breaking effect required mounts a control switch on a steering column in a position
for easy operation. In the operative positions of this switch 1, 2, 3, 4 contractors are energized to
supply current to the excitation windings of the retarder. Warning lamp is also provided on the
instrument panel to indicate when the retarder is energized. This provides a safe guard for the
driver against leaving the unit energized when the vehicle is stationary.

14
Chapter 7
ADVANTAGES
 Less maintenance
 Wide range of braking force available within the temperature limit
 Prolonged braking is possible
 Long life
 Less strain to the operation
 Smooth retardation, which cuts down, the tire wears
Eddy current brakes offer smooth retardation of vehicles without skidding. It is totally free of wear
and tear. So, it has long life compared to ordinary brakes. These need less maintenance.
In mountain areas continuous braking is needed for a long time. At this condition, eddy current
braking is more suitable to function without overheating.
By changing the excitation current to the field winding, i.e. by adjusting the position of the control
switch, we can vary the braking force to required range. The operation of eddy current brake is
very simple. i.e. the control switch is a soft switch which can be operated without any strain.
Eddy current brakes works even under the toughest environmental conditions. For example, in
larger water slides and water coasters where the humidity would immediately result in reduction
of friction and thus impair the effectiveness of ordinary brakes. It works even in highly corrosive
environments and heavily contaminated areas.

15
Chapter 8
DISADVANTAGES
 No breaking force at rest
 Need of electric power
The main disadvantage of the eddy current brake is that it needs electric power to work. Researches
are going on to overcome this disadvantage by making the brake regenerative i.e. by converting
the kinetic energy of the vehicle into electric energy and storing it back into the battery.

16
Chapter 9
APPLICATION
 For additional safety on long decants in mountain area
 For high speed passenger and goods vehicle
Eddy current brakes are best substitutes for ordinary brakes, which are being used nowadays in
road vehicles even in trains, because of their jerk-free operation. In mountain areas where
continuous braking force is needed, for a long time, the eddy current braking is very much useful
for working without overheating. Eddy current brakes are very much useful for high-speed
passengers and good vehicles. It can also be used to slow down the trolleys of faster roller coasters.

17
CONCLUSION
Eddy current brakes are the best choice when demands for reliability and safety are the highest.
They work even in the toughest environmental conditions. Even the strike of lightning will not
result in the loss of the braking force.
Eddy current braking system is not popular now a days. But we hope that the eddy current braking
system which is simpler and more effective will take the place of the ordinary braking system and
we can do expect it to be the norm one in few years of time.

18
REFERENCES
1. Manual 1 Gonzalez, Volume 25, Issue 4, July 2004
2. IEEE Transactions on magnetics, Volume 34, Issue 4, July 1998
3. Analysis of eddy current brake for high-speed railway by Wang.P.J.& Chiuch.S.J.
4. Automobile electrical equipment’s by Young &Griffith.
5. Automatic engineering by Kripal Sing.
6. Clutches and brakes by William.C.Orthwin.
7. www.reelectromagneticbrakes.com
8. www.lineareddycurrentbrakes.com

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